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Thormann W, Mosher RA. Mobilization in two-step capillary isoelectric focusing: Concepts assessed by computer simulation. Electrophoresis 2024; 45:618-638. [PMID: 38115749 DOI: 10.1002/elps.202300218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/26/2023] [Accepted: 12/07/2023] [Indexed: 12/21/2023]
Abstract
The mobilization step in a two-step capillary isoelectric focusing protocol is discussed by means of dynamic computer simulation data for systems without and with spacer compounds that establish their zones at the beginning and end of the focusing column. After focusing in an electroosmosis-free environment (first step), mobilization (second step) can be induced electrophoretically, by the application of a hydrodynamic flow, or by a combination of both means. Dynamic simulations provide insight into the complexity of the various modes of electrophoretic mobilization and dispersion associated with hydrodynamic mobilization. The data are discussed together with the relevant literature.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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2
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Pargätzi G, Bergadano A, Spadavecchia C, Theurillat R, Thormann W, Levionnois OL. Stereoselective Pharmacokinetics of Ketamine Administered at a Low Dose in Awake Dogs. Animals (Basel) 2024; 14:1012. [PMID: 38612251 PMCID: PMC11011119 DOI: 10.3390/ani14071012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 03/12/2024] [Accepted: 03/20/2024] [Indexed: 04/14/2024] Open
Abstract
The present study aimed to examine the stereoselective pharmacokinetics of racemic ketamine in dogs at low doses. The secondary aims were to identify associated behavioural effects and propose a ketamine infusion rate. The study was conducted on nine intact male beagles, with each dog undergoing two treatments (BOL and INF). For treatment BOL, an intravenous bolus of 1 mg/kg was administered over 2 min. The treatment INF involved an initial bolus of 0.5 mg/kg given over 1 min, followed by an infusion at 0.01 mg/kg/min for 1 h. Blood samples were collected for pharmacokinetic analysis. The median R/S enantiomer ratio of ketamine remained close to 1 throughout the study. Levels of S-norketamine were significantly higher than those of R-norketamine across all time points. Based on the collected data, the infusion rate predicted to achieve a steady-state racemic ketamine plasma concentration of 150 ng/mL was 0.028 mg/kg/min. Higher scores for behavioural effects were observed within the first five minutes following bolus administration. The most common behaviours observed were disorientation, head movements and staring eyes. Furthermore, employing ROC curve analysis, a racemic ketamine plasma concentration of 102 ng/mL was defined as the cut-off value, correlating with the occurrence of undesirable behavioural patterns.
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Affiliation(s)
- Gwenda Pargätzi
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland
- Clinic for Small Animals, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland
| | - Alessandra Bergadano
- Section of Occupational Safety, Health Protection and Environmental Safety, Department for Biomedical Research, University of Bern, 3008 Bern, Switzerland
| | - Claudia Spadavecchia
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland
| | - Regula Theurillat
- Institute for Infectious Diseases, University of Bern, 3001 Bern, Switzerland
- Department of Clinical Chemistry, Inselspital, Bern University Hospital, 3010 Bern, Switzerland
| | - Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, 3001 Bern, Switzerland
| | - Olivier L. Levionnois
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland
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Sandbaumhüter FA, Aerts JT, Theurillat R, Andrén PE, Thormann W, Jansson ET. Enantioselective CE-MS analysis of ketamine metabolites in urine. Electrophoresis 2023; 44:125-134. [PMID: 36398998 PMCID: PMC10108174 DOI: 10.1002/elps.202200175] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 11/16/2022] [Accepted: 11/17/2022] [Indexed: 11/21/2022]
Abstract
The chiral drug ketamine has long-lasting antidepressant effects with a fast onset and is also suitable to treat patients with therapy-resistant depression. The metabolite hydroxynorketamine (HNK) plays an important role in the antidepressant mechanism of action. Hydroxylation at the cyclohexanone ring occurs at positions 4, 5, and 6 and produces a total of 12 stereoisomers. Among those, the four 6HNK stereoisomers have the strongest antidepressant effects. Capillary electrophoresis with highly sulfated γ-cyclodextrin (CD) as a chiral selector in combination with mass spectrometry (MS) was used to develop a method for the enantioselective analysis of HNK stereoisomers with a special focus on the 6HNK stereoisomers. The partial filling approach was applied in order to avoid contamination of the MS with the chiral selector. Concentration of the chiral selector and the length of the separation zone were optimized. With 5% highly sulfated γ-CD in 20 mM ammonium formate with 10% formic acid and a 75% filling the four 6HNK stereoisomers could be separated with a resolution between 0.79 and 3.17. The method was applied to analyze fractionated equine urine collected after a ketamine infusion and to screen the fractions as well as unfractionated urine for the parent drug ketamine and other metabolites, including norketamine and dehydronorketamine.
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Affiliation(s)
| | - Jordan T Aerts
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Per E Andrén
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden.,Science for Life Laboratory, Spatial Mass Spectrometry, Uppsala University, Uppsala, Sweden
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Erik T Jansson
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
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Thormann W. Electrophoretic mobilization in capillary isoelectric focusing by a weak acid or an acidic ampholyte as catholyte assessed by computer simulation. Electrophoresis 2022; 44:656-666. [PMID: 36448503 DOI: 10.1002/elps.202200262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/19/2022] [Accepted: 11/26/2022] [Indexed: 12/05/2022]
Abstract
Capillary isoelectric focusing (CIEF) with cationic electrophoretic mobilization induced via replacing the catholyte with the anolyte or a solution of another acid or amino acid was investigated by computer simulation for a wide range pH gradient bracketed between two amphoteric spacers and short electrode vials with a higher id than the capillary. Dynamic simulations provide insight into the complexity of the mobilizing process in a hitherto inaccessible way. The electrophoretic mobilizing process begins with the penetration of the mobilizing compound through the entire capillary, is followed by a gradual or steplike decrease of pH, and ends in an environment with a non-homogenous solution of the mobilizer. Analytes do not necessarily pass the point of detection in the order of decreasing pI values. Cationic mobilization encompasses an inherent zone dispersing and refocusing process toward the capillary end. This behavior is rather strong with phosphoric acid and citric acid, moderate with aspartic acid, glutamic acid (GLU), formic acid, and acetic acid and less pronounced in the absence of the cathodic spacer. The data reveal that optical detectors should not be placed before 90% of capillary length. Aspartic acid, GLU, formic acid, and acetic acid provide an environment with a continuously decreasing pH that explains their successful use in optimized two-step CIEF protocols.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases University of Bern Bern Switzerland
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Takácsi-Nagy A, Kilár F, Thormann W. The effect of pH adjusted electrolytes on capillary isoelectric focusing assessed by high-resolution dynamic computer simulation. Electrophoresis 2021; 43:669-678. [PMID: 34894352 PMCID: PMC9306543 DOI: 10.1002/elps.202100367] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 11/10/2022]
Abstract
The effect of the composition of electrolytes on capillary IEF is assessed for systems with carrier ampholytes covering two pH units and with catholytes of decreased pH, anolytes of increased pH, and both electrode solutions with adjusted pH values. For electrolytes composed of formic acid as anolyte and ammonium hydroxide as catholyte, simulation is demonstrated to provide the expected IEF system in which analytes with pI values within the formed pH gradient are focused and become immobile. Addition of formic acid to the catholyte results in the formation of an isotachophoretic zone structure that migrates toward the cathode. With ammonium hydroxide added to the anolyte migration occurs toward the anode. In the two cases, all carrier components and amphoteric analytes migrate isotachophoretically as cations or anions, respectively. The data reveal that millimolar amounts of a counter ion are sufficient to convert an IEF pattern into an ITP system. With increasing amounts of the added counter ion, the overall length of the migrating zone structure shrinks, the range of the pH gradient changes, and the migration rate increases. The studied examples indicate that systems of this type reported in the literature should be classified as ITP and not IEF. When both electrolytes are titrated, a non-uniform background electrolyte composed of formic acid and ammonium hydroxide is established in which analytes migrate according to local pH and conductivity without forming IEF or ITP zone structures. Simulation data are in qualitative agreement with previously published experimental data.
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Affiliation(s)
- Anna Takácsi-Nagy
- Faculty of Pharmacy,Institute of Pharmaceutical Technology and Biopharmacy, University of Pécs, Pécs, Hungary
| | - Ferenc Kilár
- Institute of Bioanalysis, Medical School and Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Theurillat R, Stirnimann G, Wenker C, Hoby S, Thormann W. Aspects of albendazole metabolism in western lowland gorillas (
Gorilla gorilla gorilla
) compared to humans and other species assessed by HPLC, LC‐MS, and chiral electrokinetic chromatography. Separation Science Plus 2021. [DOI: 10.1002/sscp.202100024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory Institute for Infectious Diseases University of Bern Bern Switzerland
| | - Guido Stirnimann
- University Clinic for Visceral Surgery and Medicine University Hospital Inselspital and University of Bern Bern Switzerland
| | | | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory Institute for Infectious Diseases University of Bern Bern Switzerland
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Thormann W, Mosher RA. Dynamic computer simulations of electrophoresis: 2010-2020. Electrophoresis 2021; 43:10-36. [PMID: 34287996 PMCID: PMC9292373 DOI: 10.1002/elps.202100191] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/12/2021] [Accepted: 07/15/2021] [Indexed: 02/05/2023]
Abstract
The transport of components in liquid media under the influence of an applied electric field can be described with the continuity equation. It represents a nonlinear conservation law that is based upon the balance laws of continuous transport processes and can be solved in time and space numerically. This procedure is referred to as dynamic computer simulation. Since its inception four decades ago, the state of dynamic computer simulation software and its use has progressed significantly. Dynamic models are the most versatile tools to explore the fundamentals of electrokinetic separations and provide insights into the behavior of buffer systems and sample components of all electrophoretic separation methods, including moving boundary electrophoresis, CZE, CGE, ITP, IEF, EKC, ACE, and CEC. This article is a continuation of previous reviews (Electrophoresis 2009, 30, S16–S26 and Electrophoresis 2010, 31, 726–754) and summarizes the progress and achievements made during the 2010 to 2020 time period in which some of the existing dynamic simulators were extended and new simulation packages were developed. This review presents the basics and extensions of the three most used one‐dimensional simulators, provides a survey of new one‐dimensional simulators, outlines an overview of multi‐dimensional models, and mentions models that were briefly reported in the literature. A comprehensive discussion of simulation applications and achievements of the 2010 to 2020 time period is also included.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Sandbaumhüter FA, Gittel C, Larenza-Menzies MP, Theurillat R, Thormann W, Braun C. Stereoselective methadone disposition after administration of racemic methadone to anesthetized Shetland ponies assessed by capillary electrophoresis. Electrophoresis 2021; 42:1826-1831. [PMID: 33978252 PMCID: PMC8518386 DOI: 10.1002/elps.202100115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/04/2021] [Accepted: 05/08/2021] [Indexed: 11/23/2022]
Abstract
The enantioselectivity of the pharmacokinetics of methadone was investigated in anesthetized Shetland ponies after a single intravenous (0.5 mg/kg methadone hydrochloride; n = 6) or constant rate infusion (0.25 mg/kg bolus followed by 0.25 mg/kg/h methadone hydrochloride; n = 3) administration of racemic methadone. Plasma concentrations of l‐methadone and d‐methadone and their major metabolites, l‐ and d‐2‐ethylidene‐1,5‐dimethyl‐3,3‐diphenylpyrrolidine (EDDP), respectively, were analyzed by CE with highly sulfated γ‐cyclodextrin as chiral selector and electrokinetic analyte injection from liquid/liquid extracts prepared at alkaline pH. In both trials, the d‐methadone concentrations were lower than those of l‐methadone and the d‐EDDP levels were lower than those of L‐EDDP. For the case of a single intravenous bolus injection, the plasma concentration versus time profile of methadone enantiomers was analyzed with a two‐compartment pharmacokinetic model. l‐methadone showed a slower elimination rate constant, a lower body clearance, and a smaller steady‐state volume of distribution than d‐methadone. d‐methadone and d‐EDDP were eliminated faster than their respective l‐enantiomers. This is the first study that outlines that the disposition of racemic methadone administered to anesthetized equines is enantioselective.
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Affiliation(s)
- Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Claudia Gittel
- Department for Horses, University of Leipzig, Leipzig, Germany
| | - M Paula Larenza-Menzies
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Christina Braun
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
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Caslavska J, Thormann W. Bioanalysis of drugs and their metabolites by chiral electromigration techniques (2010-2020). Electrophoresis 2021; 42:1744-1760. [PMID: 33570170 DOI: 10.1002/elps.202000383] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Revised: 02/03/2021] [Accepted: 02/04/2021] [Indexed: 12/11/2022]
Abstract
The further development and application of capillary electromigration techniques for the enantioselective determination of drugs and their metabolites in body fluids, tissues, and in vitro preparations during the 2010 to 2020 time period continued to proof their usefulness and attractiveness in bioanalysis. This review discusses the principles and important aspects of capillary electrophoresis- based chiral drug bioassays, provides a survey of the assays reported during the past 10 years and presents an overview of the key achievements encountered in that time period. For systems with charged chiral selectors, special attention is paid on assays that feature field-amplified sample injection to enable the determination of ppb levels of analytes and optimized online incubation procedures for the rapid assessment of a metabolic pathway. Applications discussed encompass the pharmacokinetics of drug enantiomers in vivo and in vitro, the impact of inhibitors on metabolic steps, the elucidation of the stereoselectivity of drug metabolism in vivo and in vitro, and drug enantiomers in toxicological, forensic, and doping analysis.
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Affiliation(s)
- Jitka Caslavska
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Abstract
The market share of single-enantiomer drugs is steadily increasing. The pharmacodynamics and pharmacokinetics of individual enantiomers can differ considerably. Thus, their characteristics have to be addressed as early as possible in the development process of new pharmaceuticals. Capillary electrophoresis is a promising technique for enantioselective drug metabolism studies due to highly effective separations, minuscule consumption of sample and reagents, compatibility with a variety of detection techniques, high-throughput via automation, and the implementation of online procedures. An online method comprised of the diffusion-based mixing of cytochrome P450 3A4 with racemic ketamine, incubation of the enzyme reaction, separation of the reaction products S- and R-norketamine, and their quantification is presented in this chapter. Since diffusion is an inherent property of all molecules, the method enables the addition of virtually any compound to the reaction mixture without the need for additional optimization of the mixing conditions, and thus can be favorably used for the rapid screening of putative cytochrome P450 3A4 inhibitors.
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Affiliation(s)
- Roman Řemínek
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic.
| | - Zdeněk Glatz
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Gittel C, Schulz-Kornas E, Sandbaumhüter FA, Theurillat R, Vervuert I, Larenza Menzies MP, Thormann W, Braun C. Pharmacokinetics and pharmacodynamics of l-methadone in isoflurane-anaesthetized and mechanically ventilated ponies. Vet Anaesth Analg 2020; 48:213-222. [PMID: 33423953 DOI: 10.1016/j.vaa.2020.04.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 04/05/2020] [Accepted: 04/24/2020] [Indexed: 10/22/2022]
Abstract
OBJECTIVE To evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies. STUDY DESIGN Prospective single-group interventional study. ANIMALS A group of six healthy adult research ponies (four mares, two geldings). METHODS Ponies were sedated with intravenous (IV) detomidine (0.02 mg kg-1) and butorphanol (0.01 mg kg-1) for an unrelated study. Additional IV detomidine (0.004 mg kg-1) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg-1) and ketamine (2.2 mg kg-1). Anaesthesia was maintained with isoflurane in oxygen. Baseline readings were taken after 15 minutes of stable isoflurane anaesthesia. l-Methadone (0.25 mg kg-1) with fenpipramide (0.0125 mg kg-1) was then administered IV. Selected cardiorespiratory variables were recorded every 10 minutes and compared to baseline using the Wilcoxon signed-rank test. Adverse events were recorded. Arterial plasma samples for analysis of plasma concentrations and pharmacokinetics of l-methadone were collected throughout anaesthesia at predetermined time points. Data are shown as mean ± standard deviation or median and interquartile range (p < 0.05). RESULTS Plasma concentrations of l-methadone showed a rapid initial distribution phase followed by a slower elimination phase which is best described with a two-compartment model. The terminal half-life was 44.3 ± 18.0 minutes, volume of distribution 0.43 ± 0.12 L kg-1 and plasma clearance 7.77 ± 1.98 mL minute-1 kg-1. Mean arterial blood pressure increased from 85 (±16) at baseline to 100 (±26) 10 minutes after l-methadone/fenpipramide administration (p = 0.031). Heart rate remained constant. In two ponies fasciculations occurred at different time points after l-methadone administration. CONCLUSIONS AND CLINICAL RELEVANCE Administration of a l-methadone/fenpipramide combination to isoflurane anaesthetized ponies led to a transient increase in blood pressure without concurrent increases in heart rate. Pharmacokinetics of l-methadone were similar to those reported for conscious horses administered racemic methadone.
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Affiliation(s)
- Claudia Gittel
- Department for Horses, University of Leipzig, Leipzig, Germany; Queen's Veterinary School Hospital, University of Cambridge, Cambridge, UK.
| | - Ellen Schulz-Kornas
- Max Planck Weizmann Center for Integrative Archaeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Ingrid Vervuert
- Institute of Animal Nutrition, Nutrition Diseases and Dietetics, University of Leipzig, Leipzig, Germany
| | - M Paula Larenza Menzies
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Christina Braun
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
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Thormann W, Mosher RA. Instabilities of the pH gradient in carrier ampholyte-based isoelectric focusing: Elucidation of the contributing electrokinetic processes by computer simulation. Electrophoresis 2020; 42:814-833. [PMID: 33184847 DOI: 10.1002/elps.202000269] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/22/2020] [Accepted: 11/05/2020] [Indexed: 11/05/2022]
Abstract
Electrokinetic processes that lead to pH gradient instabilities in carrier ampholyte-based IEF are reviewed. In addition to electroosmosis, there are four of electrophoretic nature, namely (i) the stabilizing phase with the plateau phenomenon, (ii) the gradual isotachophoretic loss of carrier ampholytes at the two column ends in presence of electrode solutions, (iii) the inequality of the mobilities of positively and negatively charged species of ampholytes, and (iv) the continuous penetration of carbonate from the catholyte into the focusing column. The impact of these factors to cathodic and anodic drifts was analyzed by simulation of carrier ampholyte-based focusing in closed and open columns. Focusing under realistic conditions within a 5 cm long capillary in which three amphoteric low molecular mass dyes were focused in a pH 3-10 gradient formed by 140 carrier ampholytes was investigated. In open columns, electroosmosis displaces the entire gradient toward the cathode or anode whereas the electrophoretic processes act bidirectionally with a transition around pH 4 (drifts for pI > 4 and pI < 4 typically toward the cathode and anode, respectively). The data illustrate that focused zones of carrier ampholytes have an electrophoretic flux and that dynamic simulation can be effectively used to assess the magnitude of each of the electrokinetic destabilizing factors and the resulting drift for a combination of these effects. Predicted drifts of focused marker dyes are compared to those observed experimentally in a setup with coated capillary and whole column optical imaging.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Caslavska J, Mosher RA, Thormann W. Computer simulation of the isotachophoretic migration and separation of norpseudoephedrine stereoisomers with a free or immobilized neutral chiral selector. J Chromatogr A 2020; 1623:461176. [PMID: 32505280 DOI: 10.1016/j.chroma.2020.461176] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/24/2020] [Accepted: 04/27/2020] [Indexed: 11/27/2022]
Abstract
A detailed computer simulation study of the isotachophoretic migration and separation of norpseudoephedrine stereoisomers for cases with the neutral selector added to the leader, immobilized to the capillary wall or support, or partially present in the separation column is presented. The electrophoretic transport of the analytes from the sampling compartment into the separation medium with the selector, the formation of a transient mixed zone, the separation dynamics of the stereoisomers with a free or immobilized selector, the dependence of the leader pH, the ionic mobility of norpseudoephedrine, the complexation constant and selector immobilization on steady-state plateau zone properties, and zone changes occurring during the transition from the chiral environment into a selector free leader are thereby visualized in a hitherto unexplored way. For the case with the selector dissolved in the leading electrolyte, simulation data are compared to those observed in experimental setups with coated fused-silica capillaries that feature minimized electroosmosis and zone detection with conductivity and absorbance detectors.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
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15
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Caslavska J, Thormann W. Contemporary chiral simulators for capillary zone electrophoresis. Electrophoresis 2019; 41:502-513. [PMID: 31702052 DOI: 10.1002/elps.201900363] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/25/2019] [Accepted: 11/01/2019] [Indexed: 11/09/2022]
Abstract
For separation of enantiomers in presence of a chiral selector, data obtained with the 1D dynamic simulators SIMUL5complex and GENTRANS are compared to data predicted by PeakMaster 6, a recently released generalized model of the linear theory of electromigration. Four electrophoretic systems with stereoisomers of weak bases were investigated. They deal with the estimation of input data for complexation together with the elucidation of the origin of observed system peaks, the interference of analyte and system peak migration, the change of enantiomer migration order as function of the selector concentration and the inversion of analyte migration direction in presence of a multiply negatively charged selector. For all systems, data predicted with PeakMaster 6 are in agreement with those of the dynamic simulators and simulation data compare well with experimental data that were monitored with setups featuring conductivity and/or UV absorbance detection along the capillary. SIMUL5complex and GENTRANS provide the full dynamics of any buffer and sample arrangement and require very long execution time intervals. PeakMaster 6 is restricted to conventional CZE, is based on an approximate solution of the transport equations, provides data for realistic experimental conditions within seconds and represents a practical tool for an experimentalist.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Caslavska J, Schild C, Thormann W. High-resolution capillary zone electrophoresis and mass spectrometry for distinction of undersialylated and hypoglycosylated transferrin glycoforms in body fluids. J Sep Sci 2019; 43:241-257. [PMID: 31605446 DOI: 10.1002/jssc.201900857] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/01/2019] [Accepted: 10/09/2019] [Indexed: 12/21/2022]
Abstract
High-resolution capillary zone electrophoresis is used to distinguish transferrin glycoforms present in human serum, cerebrospinal fluid, and serum treated with neuraminidase and N-glycosidase F. The obtained data are compared to mass spectrometry data from the literature. The main focus is on the analysis of the various asialo-transferrin, monosialo-transferrin, and disialo-transferrin molecules found in these samples. The features of capillary zone electrophoresis and mass spectrometry are reviewed and highlighted in the context of the analysis of undersialylated and hypoglycosylated transferrin molecules. High-resolution capillary zone electrophoresis represents an effective tool to assess the diversity of transferrin patterns whereas mass spectrometry is the method of choice to elucidate structural identification about the glycoforms. Hypoglycosylated transferrin glycoforms present in sera of alcohol abusers and normal subjects are structurally identical to those in sera of patients with a congenital disorder of glycosylation type I. Asialo-transferrin, monosialo-transferrin and disialo-transferrin observed in sera of patients with a type II congenital disorder of glycosylation or a hemolytic uremic syndrome, in cerebrospinal fluid and after treatment of serum with neuraminidase are undersialylated transferrin glycoforms with two N-glycans of varying structure. Undersialylated disialo-transferrin is also observed in sera with high levels of trisialo-transferrin.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Christof Schild
- Institute of Clinical Chemistry, Inselspital, University Hospital and University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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17
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Diez Bernal S, Studer N, Thormann W, Spadavecchia C, Levionnois O. Pharmacokinetic-pharmacodynamic modelling of the antinociceptive effect of a romifidine infusion in standing horses. Vet Anaesth Analg 2019; 47:129-136. [PMID: 31810766 DOI: 10.1016/j.vaa.2019.06.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 05/16/2019] [Accepted: 06/18/2019] [Indexed: 01/23/2023]
Abstract
OBJECTIVE To evaluate the effect of a romifidine infusion on antinociception and sedation, and to investigate its relationship with plasma concentration. STUDY DESIGN Prospective, experimental, nonrandomized trial. ANIMALS A total of 10 healthy adult warmblood horses. METHODS Romifidine (loading dose: 0.08 mg kg-1, infusion: 0.03 mg kg-1 hour-1) was administered intravenously over 120 minutes. Romifidine plasma concentrations were determined by capillary electrophoresis. Sedation quality and nociceptive thresholds were evaluated at regular time points before, during and after romifidine administration. The nociceptive withdrawal reflex was elicited by electrical stimulation at the thoracic limb using a dedicated threshold tracking algorithm and recorded by electromyography at the deltoid muscle. A pharmacokinetic-pharmacodynamic model was established and correlation between romifidine plasma concentration and main output variables tested. RESULTS A two compartmental model best described the romifidine pharmacokinetic profile. The nociceptive thresholds increased compared with baseline in all horses from 10 to 146 minutes after romifidine administration (p < 0.001). Peak effect reached 5.7 ± 2.3 times the baseline threshold (mean ± standard deviation). The effect/concentration relationship followed a counter-clockwise hysteresis loop. The mean plasma concentration was weakly correlated to nociceptive thresholds (p < 0.0071, r = 0.392). The sedative effects were significant until 160 minutes but variable, not correlated to plasma concentration (p = 0.067), and weakly correlated to nociceptive thresholds (p < 0.0001, r = 0.33). CONCLUSIONS AND CLINICAL RELEVANCE Romifidine elicited a marked antinociceptive effect. Romifidine-induced antinociception appeared with a delayed onset and lasted longer than sedation after discontinuing its administration.
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Affiliation(s)
- Sabina Diez Bernal
- Department of Anaesthesiology and Pain Therapy, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
| | - Nicole Studer
- Department of Anaesthesiology and Pain Therapy, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Claudia Spadavecchia
- Department of Anaesthesiology and Pain Therapy, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Olivier Levionnois
- Department of Anaesthesiology and Pain Therapy, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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18
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Theurillat R, Sandbaumhüter FA, Gittel C, Larenza Menzies MP, Braun C, Thormann W. Enantioselective capillary electrophoresis for pharmacokinetic analysis of methadone and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in equines anesthetized with ketamine and isoflurane. Electrophoresis 2019; 40:1959-1965. [PMID: 30900259 DOI: 10.1002/elps.201900044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 03/18/2019] [Accepted: 03/18/2019] [Indexed: 01/30/2023]
Abstract
An enantioselective assay for the determination of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in equine plasma based on capillary electrophoresis with highly sulfated γ-cyclodextrin as chiral selector and electrokinetic analyte injection is described. The assay is based on liquid/liquid extraction of the analytes at alkaline pH from 0.1 mL plasma followed by electrokinetic sample injection of the analytes from the extract across a buffer plug without chiral selector. Separation occurs cationically at normal polarity in a pH 3 phosphate buffer containing 0.16% (w/v) of highly sulfated γ-cyclodextrin. The developed assay is precise (intra- and interday RSD < 4% and < 7%, respectively), is capable to determine enantiomer levels of methadone and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in plasma down to 2.5 ng/mL, and was successfully applied to monitor enantiomer drug and metabolite levels in plasma of a pony that was anesthetized with racemic ketamine and isoflurane and received a bolus of racemic methadone and a bolus followed by constant rate infusion of racemic methadone. The data suggest that the assay is well suited for pharmacokinetic purposes.
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Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Claudia Gittel
- Department for Horses, University of Leipzig, Leipzig, Germany
| | - M Paula Larenza Menzies
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
| | - Christina Braun
- Clinical Unit of Anaesthesiology and Perioperative Intensive-Care Medicine, Vetmeduni Vienna, Vienna, Austria
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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19
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Mikkonen S, Caslavska J, Gebauer P, Thormann W. Inverse cationic ITP for separation of methadone enantiomers with sulfated β-cyclodextrin as chiral selector. Electrophoresis 2018; 40:659-667. [PMID: 30311251 DOI: 10.1002/elps.201800387] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 10/03/2018] [Accepted: 10/10/2018] [Indexed: 12/17/2022]
Abstract
Chiral ITP of the weak base methadone using inverse cationic configurations with H+ as leading component and multiple isomer sulfated β-CD (S-β-CD) as leading electrolyte (LE) additive, has been studied utilizing dynamic computer simulation, a calculation model based on steady-state values of the ITP zones, and capillary ITP. By varying the amount of acidic S-β-CD in the LE composed of 3-morpholino-2-hydroxypropanesulfonic acid and the chiral selector, and employing glycylglycine as terminating electrolyte (TE), inverse cationic ITP provides systems in which either both enantiomers, only the enantiomer with weaker complexation, or none of the two enantiomers form cationic ITP zones. For the configuration studied, the data reveal that only S-methadone migrates isotachophoretically when the S-β-CD concentration in the LE is between about 0.484 and 1.113 mM. Under these conditions, R-methadone migrates zone electrophoretically in the TE. An S-β-CD concentration between about 0.070 and 0.484 mM results in both S- and R-methadone forming ITP zones. With >1.113 mM and < about 0.050 mM of S-β-CD in the LE both enantiomers are migrating within the TE and LE, respectively. Chiral inverse cationic ITP with acidic S-β-CD in the LE is demonstrated to permit selective ITP trapping and concentration of the less interacting enantiomer of a weak base.
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Affiliation(s)
- Saara Mikkonen
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.,Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Petr Gebauer
- Institute of Analytical Chemistry of the Czech Academy of Sciences, Brno, Czech Republic
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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20
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Kummer M, Šestáková N, Theurillat R, Huynh-Do U, Endimiani A, Sendi P, Thormann W. Monitoring of cefepime in urine by micellar electrokinetic capillary chromatography with ultraviolet detection and liquid chromatography coupled to mass spectrometry. J Sep Sci 2018; 41:4067-4074. [PMID: 30198147 DOI: 10.1002/jssc.201800763] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 09/01/2018] [Accepted: 09/03/2018] [Indexed: 11/06/2022]
Abstract
Cefepime monitoring in urine by micellar electrokinetic capillary chromatography with UV detection and liquid chromatography coupled to mass spectrometry via electrospray ionization is described. For micellar electrokinetic capillary chromatography, sample preparation comprised urine dilution and dodecyl-sulfate protein precipitation at pH 4.5, whereas diluted urines were analyzed in the other assay. Both approaches provided suitable conditions for cefepime analysis in urines of healthy volunteers that were spiked with cefepime. Cefepime monitoring by micellar electrokinetic capillary chromatography in samples from patients taking multiple drugs were prone to interferences, whereas liquid chromatography coupled to mass spectrometry provided clean chromatograms and thus selective detection of cefepime in all samples. The latter assay was used to measure urinary cefepime in a prospective pilot study and to assess cefepime stability in urines at 25, 4, -20 and -70°C. The data suggest that urinary cefepime is stable for at least 72 h at all tested temperatures.
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Affiliation(s)
- Mirjam Kummer
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Nela Šestáková
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Uyen Huynh-Do
- Department of Nephrology and Hypertension, University Hospital Bern, University of Bern, Bern, Switzerland
| | - Andrea Endimiani
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Parham Sendi
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland.,Department of Infectious Diseases, University Hospital Bern, Bern, Switzerland.,Department of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, University Basel, Basel, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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21
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Tobler M, Caslavska J, Burda P, Thormann W. High-resolution capillary zone electrophoresis for transferrin glycoform analysis associated with congenital disorders of glycosylation. J Sep Sci 2018; 41:2808-2818. [PMID: 29701302 DOI: 10.1002/jssc.201800082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 04/18/2018] [Accepted: 04/19/2018] [Indexed: 11/10/2022]
Abstract
High-resolution capillary zone electrophoresis is used to assess the transferrin profile in serum of patients with eight different congenital disorders of glycosylation that represent type I, type II, and mixed type I/II disorders. Capillary zone electrophoresis data are compared to patterns obtained by gel isoelectric focusing. The high-resolution capillary zone electrophoresis method is shown to represent an effective tool to assess the diversity of transferrin patterns. Hypoglycosylated disialo-, monosialo-, and asialo-transferrin in type I cases can be distinguished from the corresponding underdesialylated transferrin glycoforms present in type II disorders. The latter can be separated from and detected ahead of their corresponding hypoglycosylated forms of type I patients. Both types of glycoforms are detected in sera of mixed type I/II patients. The assay has the potential to be used as screening method for congenital disorders of glycosylation. It can be run with a few microliters of serum when microvials are used.
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Affiliation(s)
- Micha Tobler
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Patricie Burda
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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22
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Šesták J, Theurillat R, Sandbaumhüter FA, Thormann W. Fundamental aspects of field-amplified electrokinetic injection of cations for enantioselective capillary electrophoresis with sulfated cyclodextrins as selectors. J Chromatogr A 2018; 1558:85-95. [PMID: 29759647 DOI: 10.1016/j.chroma.2018.05.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/02/2018] [Accepted: 05/08/2018] [Indexed: 01/30/2023]
Abstract
Head-column field-amplified sample stacking of cations from a low conductivity sample followed by enantiomeric separation using negatively charged chiral selectors was studied experimentally and with computer simulation. Aspects investigated include the direct electrokinetic injection of the analytes into the background electrolyte, the use of a selector free buffer plug, the contribution of complexation within the buffer plug and the application of an additional water plug between sample and buffer plug. Attention was paid for changes of ionic strength which is known to have a significant impact on complexation and thus effective mobility. Racemic methadone was selected as a model compound, randomly substituted sulfated β-cyclodextrin as chiral selector and phosphate buffers (pH 6.3) for the background electrolyte and the buffer plug. Results confirm that the buffer plug is providing a spacer between cationic analytes and the negatively charged selector during electrokinetic injection. Simulation predicts the required length and composition of the plug for a given injection time to avoid an interference with the selector. A short water plug added between the low conductivity sample and a high conductivity buffer plug is demonstrated to provide best conditions to achieve high sensitivity in enantioselective drug assays with sulfated cyclodextrins as selectors.
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Affiliation(s)
- Jozef Šesták
- University of Bern, Clinical Pharmacology Laboratory, Institute for Infectious Diseases, Murtenstrasse 35, 3008 Bern, Switzerland; Institute of Analytical Chemistry of the Czech Academy of Sciences, Veveří 97, 602 00 Brno, Czechia
| | - Regula Theurillat
- University of Bern, Clinical Pharmacology Laboratory, Institute for Infectious Diseases, Murtenstrasse 35, 3008 Bern, Switzerland
| | - Friederike A Sandbaumhüter
- University of Bern, Clinical Pharmacology Laboratory, Institute for Infectious Diseases, Murtenstrasse 35, 3008 Bern, Switzerland
| | - Wolfgang Thormann
- University of Bern, Clinical Pharmacology Laboratory, Institute for Infectious Diseases, Murtenstrasse 35, 3008 Bern, Switzerland.
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23
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Mikkonen S, Thormann W. Computer simulation of the enantioselective separation of weak bases in an online capillary electrophoresis based microanalysis configuration comprising sulfated cyclodextrin as selector. Electrophoresis 2018; 39:1482-1487. [PMID: 29645297 DOI: 10.1002/elps.201800113] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 03/29/2018] [Accepted: 04/03/2018] [Indexed: 11/10/2022]
Abstract
Computer simulation was utilized to characterize the electrophoretic processes occurring after reactant mixing in an online assay format used for monitoring the enantioselective N-demethylation of ketamine to norketamine in the presence of highly sulfated γ-cyclodextrin (HS-γ-CD). The incubated reaction mixture (at pH 7.4 and without chiral selector) is bracketed by a low pH BGE containing 2% HS-γ-CD as chiral selector, thereby forming a discontinuous buffer system. Upon power application, simulation provides insight into the formation of moving boundaries and new zones together with the prediction of the behavior of ketamine and norketamine enantiomers. The analytes first migrate cationically in a zone electrophoretic manner until they come in contact with HS-γ-CD upon which enantioseparation is initiated. Complexation has a focusing effect and the electrophoretic transport becomes reversed, that is, toward the anode. Simulation revealed that the initial conditions for the chiral separation, including buffer components concentrations, pH, and ionic strength, are different than those in the BGE. As a consequence thereof, the experimentally determined complexation parameters for the BGE were unable to correctly describe the migration behavior of the analytes in this column section. An increase in the input binding constants by a factor of two to four, as a result of the decreased ionic strength, resulted in simulation data that agreed with experimental findings.
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Affiliation(s)
- Saara Mikkonen
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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24
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Sandbaumhüter FA, Thormann W. Enantioselective capillary electrophoresis provides insight into the phase II metabolism of ketamine and its metabolites in vivo and in vitro. Electrophoresis 2018; 39:1478-1481. [PMID: 29572863 DOI: 10.1002/elps.201800012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 02/23/2018] [Accepted: 03/08/2018] [Indexed: 01/31/2023]
Abstract
Glucuronidation catalyzed by uridine-5'-diphospho-glucuronosyl-transferases (UGTs) is the most important reaction in phase II metabolism of drugs and other compounds. O-glucuronidation is more common than N-glucuronidation. The anesthetic, analgesic and antidepressive drug ketamine is metabolized in phase I by cytochrome P450 enzymes to norketamine, hydroxynorketamine (HNK) diastereomers and dehydronorketamine (DHNK). Equine urine samples collected two hours after ketamine injection were treated with β-glucuronidase and analyzed with three enantioselective capillary electrophoresis assays. Concentrations of HNK diastereomers and norketamine were significantly higher in comparison to untreated urine and an increase of ketamine and DHNK levels was found in selected but not all samples. This suggests that O-glucuronides of HNK and N-glucuronides of the other compounds are formed in equines. N-glucuronidation of norketamine was studied in vitro with liver microsomes of different species and the single human enzyme UGT1A4. With equine liver microsomes (ELM) a stereoselective N-glucuronidation of norketamine was found that compares well to the results obtained with urines collected after ketamine administration. No reaction was observed with canine liver microsomes, human liver microsomes and UGT1A4. Incubation of ketamine and DHNK with ELM did not reveal any glucuronidation. Enantioselective CE is suitable to provide insight into the phase II metabolism of ketamine and its metabolites.
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Affiliation(s)
- Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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25
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Sandbaumhüter FA, Vimercati S, Thormann W, Mevissen M. Role of the equine CYP3A94, CYP3A95 and CYP3A97 in ketamine metabolism in presence of medetomidine, diazepam and methadone studied by enantioselective capillary electrophoresis. Toxicol In Vitro 2018; 50:242-248. [PMID: 29614330 DOI: 10.1016/j.tiv.2018.03.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 01/18/2018] [Accepted: 03/30/2018] [Indexed: 12/11/2022]
Abstract
The anesthetic ketamine is often combined with analgesics and benzodiazepines in equine medicine. Therefore, drug-drug interactions are possible. Enzyme kinetics for ketamine N-demethylation were determined using equine CYP3A94, CYP3A95 and CYP3A97, and the effect of medetomidine, diazepam and methadone on the ketamine metabolism was studied in vitro. Ketamine was incubated with the CYPs or equine liver microsomes (ELM) alone or in presence of medetomidine, diazepam and/or methadone for different times. Norketamine levels were determined using enantioselective capillary electrophoresis (CE) with highly sulfated γ-cyclodextrin as chiral selector. The three equine CYPs were demonstrated to be involved in ketamine N-demethylation and the kinetics can be described with the Michaelis-Menten model. Vmax values calculated for CYP3A94 and CYP3A97 were higher than for CYP3A95. The lowest Km value was found for CYP3A94. In contrast to diazepam and methadone, the α2-recepor agonist medetomidine diminished the norketamine formation significantly in CYP3A94 and CYP3A97. In ELM, increasing concentrations of diazepam inhibited the norketamine formation. Despite the differences in ketamine N-demethylation in combination with diazepam and methadone, the effect is unlikely to be of clinical relevance because ketamine and the other drugs do not have a small therapeutic margin.
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Affiliation(s)
- Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Murtenstrasse 35, Bern 3008, Switzerland
| | - Sara Vimercati
- Veterinary Pharmacology and Toxicology, Department of Clinical research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Länggassstrasse 124, Bern 3012, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Murtenstrasse 35, Bern 3008, Switzerland
| | - Meike Mevissen
- Veterinary Pharmacology and Toxicology, Department of Clinical research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Länggassstrasse 124, Bern 3012, Switzerland.
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26
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Mikkonen S, Caslavska J, Hruška V, Thormann W. Computer simulation and enantioselective capillary electrophoresis to characterize isomer mixtures of sulfated β-cyclodextrins. Electrophoresis 2017; 39:770-778. [PMID: 29090834 DOI: 10.1002/elps.201700376] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 10/25/2017] [Accepted: 10/26/2017] [Indexed: 11/08/2022]
Abstract
The enantiomeric separation of methadone in the presence of multiple isomer mixtures of sulfated β-cyclodextrin (S-β-CD) was studied experimentally with CZE and theoretically using computer simulation. Experiments were performed over many years with several lots of S-β-CD from the same manufacturer with a specified degree of substitution of 7-11. Large differences in the migration patterns were observed between certain lots and it was concluded that the extent of labelling in lots released after a transition time was higher than originally specified. The migration pattern was observed to be associated with (i) the ionic strength increase resulting from using S-β-CDs with a higher charge state and (ii) differences in buffer composition. Apparent binding constants between methadone and the S-β-CD and complex mobilities were determined for different lots of S-β-CD at varying ionic strength using phosphate and 3-morpholino-2-hydroxypropanesulfonic acid buffers. The obtained values were used as input for simulations. For a given ionic strength, agreement between predicted and experimentally observed behavior was obtained for different buffers. R-methadone has a stronger interaction with S-β-CD than S-methadone. For any given configuration there is a distinct S-β-CD concentration range which results in the cationic migration of S-methadone while the migration direction of R-methadone is reversed. This configuration was demonstrated to be applicable for micropreparative CZE separations.
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Affiliation(s)
- Saara Mikkonen
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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27
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Caslavska J, Thormann W. Monitoring of transferrin isoforms in biological samples by capillary electrophoresis. J Sep Sci 2017; 41:303-322. [PMID: 28885776 DOI: 10.1002/jssc.201700914] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 09/04/2017] [Accepted: 09/04/2017] [Indexed: 11/10/2022]
Abstract
Work dealing with the monitoring of transferrin isoforms in human serum and other body fluids by capillary electrophoresis is reviewed. It comprises capillary zone electrophoresis and capillary isoelectric focusing efforts that led to the exploration and use of assays for the determination of carbohydrate-deficient transferrin as a marker for excessive alcohol intake, genetic variants of transferrin, congenital disorders of glycosylation and β-2-transferrin, which is a marker for cerebrospinal fluid leakage. This paper provides insight into the development, specifications, strengths, weaknesses, and routine use of the currently known capillary electrophoresis based assays suitable to detect transferrin isoforms in body fluids. The achievements reached so far indicate that capillary zone electrophoresis is an attractive technology to monitor the molecular forms of transferrin in biological specimens as the assays do not require an elaborate sample pretreatment and thus can be fully automated for high-throughput analyses on multicapillary instruments. Assays based on capillary isoelectric focusing are less attractive. They require immunoextraction of transferrin from the biological matrix and mobilization after focusing if instrumentation with a whole-column imaging detector is not available. Interactions of the carrier ampholytes with the iron of transferrin may prevent iron saturation and thus provide more complicated isoform patterns.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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28
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Šesták J, Thormann W. Insights into head-column field-amplified sample stacking: Part II. Study of the behavior of the electrophoretic system after electrokinetic injection of cationic compounds across a short water plug. J Chromatogr A 2017; 1512:124-132. [PMID: 28712552 DOI: 10.1016/j.chroma.2017.06.073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 06/23/2017] [Accepted: 06/29/2017] [Indexed: 11/18/2022]
Abstract
Part I on head-column field-amplified sample stacking comprised a detailed study of the electrokinetic injection of a weak base across a short water plug into a phosphate buffer at low pH. The water plug is converted into a low conductive acidic zone and cationic analytes become stacked at the interface between this and a newly formed phosphoric acid zone. The fundamentals of electrokinetic processes occurring thereafter were studied experimentally and with computer simulation and are presented as part II. The configuration analyzed represents a discontinuous buffer system. Computer simulation revealed that the phosphoric acid zone at the plug-buffer interface becomes converted into a migrating phosphate buffer plug which corresponds to the cationically migrating system zone of the phosphate buffer system. Its mobility is higher than that of the analytes such that they migrate behind the system zone in a phosphate buffer comparable to the applied background electrolyte. The temporal behaviour of the current and the conductivity across the water plug were monitored and found to reflect the changes in the low conductivity plug. Determination of the buffer flow in the capillary revealed increased pumping caused by the mismatch of electroosmosis within the low conductivity plug and the buffer. This effect becomes elevated with increasing water plug length. For plug lengths up to 1% of the total column length the flow quickly drops to the electroosmotic flow of the buffer and simulations with experimentally determined current and flow values predict negligible band dispersion and no loss of resolution for both low and large molecular mass components.
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Affiliation(s)
- Jozef Šesták
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Institute of Analytical Chemistry of the Czech Academy of Sciences, v. v. i., Brno, Czechia
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
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Caslavska J, Lanz C, Burda P, Tobler M, Thormann W. Analysis of genetic variants of transferrin in human serum after desialylation by capillary zone electrophoresis and capillary isoelectric focusing. J Sep Sci 2017; 40:2488-2497. [PMID: 28371325 DOI: 10.1002/jssc.201700211] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 03/21/2017] [Accepted: 03/21/2017] [Indexed: 12/31/2022]
Abstract
Capillary electrophoresis analysis of transferrin in human serum is used to assess genetic variants after desialylation with neuraminidase and iron saturation to reduce the complexity of the transferrin pattern and thus facilitate the recognition of transferrin polymorphisms. Asialo-transferrin forms are analyzed by capillary zone electrophoresis using assay conditions as for the monitoring of carbohydrate-deficient transferrin or by capillary isoelectric focusing in a pH 5-8 gradient which requires immunoextraction of transferrin prior to analysis. With the carrier ampholytes used, peaks for iron saturated and iron depleted transferrin are monitored which indicates complexation of iron ions by carrier ampholytes. For BC, CD, and BD genetic variants, the expected peaks for B, C, and D forms of transferrin were detected with both methods. Monitoring of CC patterns revealed three cases, namely those producing double peaks in both methods, a double peak in capillary isoelectric focusing only and a double peak in capillary zone electrophoresis only. For all samples analyzed, data obtained by capillary isoelectric focusing could be confirmed with gel isoelectric focusing. The two capillary electrophoresis methods are shown to represent effective tools to assess unusual transferrin patterns, including genetic variants with dissimilar abundances of the two forms.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Christian Lanz
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Patricie Burda
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Micha Tobler
- Division of Metabolism, University Children's Hospital Zürich, Zürich, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Šesták J, Thormann W. Insights into head-column field-amplified sample stacking: Part I. Detailed study of electrokinetic injection of a weak base across a short water plug. J Chromatogr A 2017; 1502:51-61. [PMID: 28460869 DOI: 10.1016/j.chroma.2017.04.041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/10/2017] [Accepted: 04/20/2017] [Indexed: 12/30/2022]
Abstract
The fundamentals of electrokinetic injection of the weak base methadone across a short water plug into a phosphate buffer at low pH were studied experimentally and with computer simulation. The current during electrokinetic injection, the formation of the analyte zone, changes occurring within and around the water plug and mass transport of all compounds in the electric field were investigated. The impact of water plug length, plug injection velocity, and composition of sample, plug and background electrolyte are discussed. Experimental data revealed that properties of sample, water plug and stacking boundary are significantly and rapidly altered during electrokinetic injection. Simulation provided insight into these changes, including the nature of the migrating boundaries and the stacking of methadone at the interface to a newly formed phosphoric acid zone. The data confirm the role of the water plug to prevent contamination of the sample by components of the background electrolyte and suggest that mixing caused by electrohydrodynamic instabilities increases the water plug conductivity. The sample conductivity must be controlled by addition of an acid to prevent generation of reversed flow which removes the water plug and to create a buffering environment. Results revealed that a large increase in background electrolyte concentration is not accompanied with a significant increase in stacking.
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Affiliation(s)
- Jozef Šesták
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Institute of Analytical Chemistry of the Czech Academy of Sciences, v. v. i., Brno, Czechia
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
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Šestáková N, Theurillat R, Sendi P, Thormann W. Monitoring of cefepime in human serum and plasma by micellar electrokinetic capillary chromatography: Improvement of sample preparation and validation by liquid chromatography coupled to mass spectrometry. J Sep Sci 2017; 40:1805-1814. [PMID: 28217952 DOI: 10.1002/jssc.201601446] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 01/31/2017] [Accepted: 02/06/2017] [Indexed: 11/06/2022]
Abstract
Cefepime monitoring in deproteinized human serum and plasma by micellar electrokinetic capillary chromatography and liquid chromatography coupled to mass spectrometry in presence of other drugs is reported. For micellar electrokinetic capillary chromatography, sample preparation comprised dodecylsulfate protein precipitation at pH 4.5 using an increased buffer concentration compared to that of a previous assay and removal of hydrophobic compounds with dichloromethane. This provided robust conditions for cefepime analysis in the presence of sulfamethoxazole and thus enabled its determination in samples of patients that receive cotrimoxazole. The liquid chromatography assay is based upon use of a column with a pentafluorophenyl-propyl modified and multiendcapped stationary phase and the coupling to electrospray ionization with a single quadrupole detector. The performances of both assays with multilevel internal calibration were assessed with calibration and control samples and both assays were determined to be robust. Cefepime levels monitored by micellar electrokinetic capillary chromatography in samples from patients that were treated with cefepime only and with cefepime and cotrimoxazole were found to compare well with those obtained by liquid chromatography coupled to mass spectrometry. Cefepime drug levels determined by micellar electrokinetic capillary chromatography could thereby be validated.
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Affiliation(s)
- Nela Šestáková
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Parham Sendi
- Department of Infectious Diseases, University Hospital of Bern, Bern, Switzerland.,Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Sandbaumhüter FA, Theurillat R, Bettschart-Wolfensberger R, Thormann W. Effect of the α2
-receptor agonists medetomidine, detomidine, xylazine, and romifidine on the ketamine metabolism in equines assessed with enantioselective capillary electrophoresis. Electrophoresis 2017; 38:1895-1904. [DOI: 10.1002/elps.201700017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 02/21/2017] [Accepted: 02/21/2017] [Indexed: 01/24/2023]
Affiliation(s)
| | - Regula Theurillat
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
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Sandbaumhüter FA, Theurillat R, Thormann W. Separation of hydroxynorketamine stereoisomers using capillary electrophoresis with sulfated β-cyclodextrin and highly sulfated γ-cyclodextrin. Electrophoresis 2017; 38:1878-1885. [PMID: 28213944 DOI: 10.1002/elps.201700016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 02/09/2017] [Accepted: 02/14/2017] [Indexed: 01/17/2023]
Abstract
The racemic N-methyl-d-aspartate receptor antagonist ketamine is used in anesthesia, analgesia and the treatment of depressive disorders. It is known that interactions of hydroxylated norketamine metabolites and 5,6-dehydronorketamine (DHNK) with the α7 -nicotinic acetylcholine receptor and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor are responsible for the antidepressive effects. Ketamine and its first metabolite norketamine are not active on these receptors. As stereoselectivity plays a role in ketamine metabolism, a cationic capillary electrophoresis based method capable of resolving and analyzing the stereoisomers of four hydroxylated norketamine metabolites, norketamine and DHNK was developed. The assay is based on liquid/liquid extraction of the analytes from the biological matrix, electrokinetic sample injection across a buffer plug and analysis of the stereoisomers in a phosphate background electrolyte (BGE) at pH 3 comprising a mixture of sulfated β-cyclodextrin (5 mg/mL) and highly sulfated γ-cyclodextrin (0.1%). The method was used to analyze samples of an in vitro study in which ketamine was incubated with equine liver microsomes and in plasma samples of dogs and horses that were collected after an i.v. bolus injection of racemic ketamine.
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Affiliation(s)
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, University of Bern, Bern, Switzerland
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Takácsi-Nagy A, Kilár F, Thormann W. Modeling of formation and prevention of a pure water zone in capillary isoelectric focusing with narrow pH range carrier ampholytes. Electrophoresis 2016; 38:677-688. [PMID: 27699824 DOI: 10.1002/elps.201600314] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 09/01/2016] [Accepted: 09/02/2016] [Indexed: 11/07/2022]
Abstract
This paper comprises a continuation of computer simulation studies dealing with carrier ampholyte based CIEF in presence of narrow pH gradients. With this technique, amphoteric sample components with pI values outside the pH gradient are migrating isotachophoretically toward the cathode or anode whereas components with pI values within the gradient become focused. In order to understand the processes occurring in presence of the electric field, the behavior of both carrier ampholytes and amphoteric sample components is investigated by computer modeling. Characteristics of two pH unit gradients with end components having pI values at or around 7.00 and conditions that lead to the formation of a water zone at neutrality were investigated. Data obtained reveal that a zone of water is formed in focusing with carrier ampholytes when the applied pH range does not cover the neutral region, ends at pH 7.00 or begins at pH 7.00. The presence of additional amphoteric components that cover the neutrality region prevent water zone formation under current flow. This situation is met in experiments with narrow pH gradients that end or begin around neutrality. Simulation data reveal that no water zone evolves when atmospheric carbon dioxide dissolved in the catholyte causes the migration of carbonic acid (in the form of carbonate and/or hydrogen carbonate ions) from the catholyte through the focusing structure. An electrolyte change in the electrode solution does not have an impact on the focusing part but does change the isotachophoretic pattern migrating behind the leading ion.
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Affiliation(s)
- Anna Takácsi-Nagy
- Institute of Bioanalysis and Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Ferenc Kilár
- Institute of Bioanalysis and Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Pelcová M, Řemínek R, Sandbaumhüter FA, Mosher RA, Glatz Z, Thormann W. Simulation and experimental study of enzyme and reactant mixing in capillary electrophoresis based on-line methods. J Chromatogr A 2016; 1471:192-200. [PMID: 27720173 DOI: 10.1016/j.chroma.2016.10.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 09/27/2016] [Accepted: 10/02/2016] [Indexed: 10/20/2022]
Abstract
The establishment of an efficient reaction mixture represents a crucial part of capillary electrophoresis based on-line enzymatic assays. For ketamine N-demethylation to norketamine mediated by the cytochrome P450 3A4 enzyme, mixing of enzyme and reactants in the incubation buffer at physiological pH was studied by computer simulation. A dynamic electrophoretic simulator that encompasses Taylor-Aris diffusivity which accounts for dispersion due to the parabolic flow profile associated with pressure driven flow was utilized. The simulator in the diffusion mode was used to predict transverse diffusional reactant mixing occurring during hydrodynamic plug injection of configurations featuring four and seven plugs. The same simulator in the electrophoretic mode was applied to study electrophoretic reactant mixing caused by voltage application in absence of buffer flow. Resulting conclusions were experimentally verified with enantioselective analysis of norketamine in a background electrolyte at low pH. Furthermore, simulations visualize buffer changes that occur upon power application between incubation buffer and background electrolyte and have an influence on the reaction mixture.
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Affiliation(s)
- Marta Pelcová
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Roman Řemínek
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Zdeněk Glatz
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
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Sandbaumhüter FA, Theurillat R, Bektas RN, Kutter AP, Bettschart-Wolfensberger R, Thormann W. Pharmacokinetics of ketamine and three metabolites in Beagle dogs under sevoflurane vs. medetomidine comedication assessed by enantioselective capillary electrophoresis. J Chromatogr A 2016; 1467:436-444. [DOI: 10.1016/j.chroma.2016.07.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 07/13/2016] [Accepted: 07/23/2016] [Indexed: 12/27/2022]
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Mikkonen S, Jacksén J, Roeraade J, Thormann W, Emmer Å. Microfluidic Isoelectric Focusing of Amyloid Beta Peptides Followed by Micropillar-Matrix-Assisted Laser Desorption Ionization-Mass Spectrometry. Anal Chem 2016; 88:10044-10051. [PMID: 27619937 DOI: 10.1021/acs.analchem.6b02324] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A novel method for preconcentration and purification of the Alzheimer's disease related amyloid beta (Aβ) peptides by isoelectric focusing (IEF) in 75 nL microchannels combined with their analysis by micropillar-matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) is presented. A semiopen chip-based setup, consisting of open microchannels covered by a lid of a liquid fluorocarbon, was used. IEF was performed in a mixture of four small and chemically well-defined amphoteric carriers, glutamic acid, aspartyl-histidine (Asp-His), cycloserine (cSer), and arginine, which provided a stepwise pH gradient tailored for focusing of the C-terminal Aβ peptides with a pI of 5.3 in the boundary between cSer and Asp-His. Information about the focusing dynamics and location of the foci of Aβ peptides and other compounds was obtained using computer simulation and by performing MALDI-MS analysis directly from the open microchannel. With the established configuration, detection was performed by direct sampling of a nanoliter volume containing the focused Aβ peptides from the microchannel, followed by deposition of this volume onto a chip with micropillar MALDI targets. In addition to purification, IEF preconcentration provides at least a 10-fold increase of the MALDI-MS-signal. After immunoprecipitation and concentration of the eluate in the microchannel, IEF-micropillar-MALDI-MS is demonstrated to be a suitable platform for detection of Aβ peptides in human cerebrospinal fluid as well as in blood plasma.
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Affiliation(s)
- Saara Mikkonen
- Department of Chemistry, Division of Applied Physical Chemistry-Analytical Chemistry, KTH Royal Institute of Technology , 10044 Stockholm, Sweden
| | - Johan Jacksén
- Department of Chemistry, Division of Applied Physical Chemistry-Analytical Chemistry, KTH Royal Institute of Technology , 10044 Stockholm, Sweden
| | - Johan Roeraade
- Department of Chemistry, Division of Applied Physical Chemistry-Analytical Chemistry, KTH Royal Institute of Technology , 10044 Stockholm, Sweden
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern , 3008 Bern, Switzerland
| | - Åsa Emmer
- Department of Chemistry, Division of Applied Physical Chemistry-Analytical Chemistry, KTH Royal Institute of Technology , 10044 Stockholm, Sweden
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Theurillat R, Joneli J, Wanzenried U, Schiess J, Hurni M, Weber T, Sendi P, Thormann W. Therapeutic drug monitoring of cefepime with micellar electrokinetic capillary chromatography: Assay improvement, quality assurance, and impact on patient drug levels. J Sep Sci 2016; 39:2626-32. [PMID: 27130081 DOI: 10.1002/jssc.201600271] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 04/15/2016] [Accepted: 04/17/2016] [Indexed: 11/05/2022]
Abstract
The improvement and performance of a micellar electrokinetic capillary chromatography assay for cefepime in human serum and plasma with a 50 μm id fused-silica capillary elongated from 40 to 60 cm is reported. Sample preparation with dodecylsulfate protein precipitation at pH 4.5, the pH 9.1 separation medium, and the applied voltage were as reported previously [16]. The change resulted in a significant lower current, higher resolution, and increased detection time intervals. The performance of the assay with multilevel internal calibration was assessed with calibration and control samples. Quality assurance data of a 2-year period assessed under the new conditions demonstrated the robustness of the assay. In serum samples of patients who received both cefepime and sulfamethoxazole, cefepime could not be detected due to the inseparability of the two compounds. The presence of an interference can be recognized by an increased peak width (width > 0.2 min), the appearance of a shoulder or an unresolved double peak. The patient data gathered during a 3-year period reveal that introduction of therapeutic drug monitoring led to a 50% reduction of the median drug level. The data suggest that therapeutic drug monitoring can help to minimize the risk of major adverse reactions and to increase drug safety on an individual basis.
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Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Jeannine Joneli
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Ursula Wanzenried
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Jeannette Schiess
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Monika Hurni
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Thomas Weber
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Parham Sendi
- Department of Infectious Diseases, University Hospital of Bern and Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Menzies MPL, Ringer SK, Conrot A, Theurillat R, Kluge K, Kutter AP, Jackson M, Thormann W, Bettschart-Wolfensberger R. Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low-dose S-ketamine or medetomidine infusions. Vet Anaesth Analg 2016; 43:623-634. [PMID: 26915545 DOI: 10.1111/vaa.12359] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 09/17/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To evaluate cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane receiving medetomidine or S-ketamine infusions. STUDY DESIGN Randomized, blinded, prospective clinical trial. ANIMALS Fifty horses undergoing elective surgery. METHODS After acepromazine and flunixin meglumine premedication, horses received medetomidine (7 μg kg-1 ) intravenously (IV). Anaesthesia was induced with midazolam and racemic ketamine (Med treatment group; 2.2 mg kg-1 ; n = 25) or S-ketamine (S-ket treatment group; 1.1 mg kg-1 ; n = 25) IV and maintained with isoflurane in oxygen/air and medetomidine (Med; 3.5 μg kg-1 hour-1 ) or S-ketamine (S-ket; 0.5 mg kg-1 hour-1 ). All horses were mechanically ventilated. Cardiopulmonary variables were evaluated. Isoflurane end-tidal concentrations (Fe'Iso), dobutamine requirements and thiopental boli were recorded. Plasma samples were collected in six horses to evaluate S-ketamine and S-norketamine concentrations. After surgery, medetomidine 2 μg kg-1 was administered IV. Four independent observers scored recovery using a visual analogue scale and a numerical rating scale. RESULTS Both groups required similar mean Fe'Iso (1%). However, S-ket horses needed more thiopental boli. Median intraoperative cardiac index values were higher with S-ket (4.5 L minute-1 m-2 ) than Med (3.9 L minute-1 m-2 ). Overall, there were no differences in heart rate, blood pressure or dobutamine requirements; however, horses in S-ket showed higher heart rate values at 30 minutes after anaesthesia induction. Compared with Med horses, S-ket horses showed decreased PaO2 and increased pulmonary venous admixture values estimated with the Fshunt calculation. Recoveries were shorter and of poorer quality with S-ket. During infusion, S-ketamine and S-norketamine plasma concentrations lay in the ranges of 0.209-0.917 μg mL-1 and 0.250-0.723 μg mL-1 , respectively. CONCLUSIONS AND CLINICAL RELEVANCE Despite the higher intraoperative cardiac index with S-ket, both protocols were considered to provide acceptable cardiovascular function. However, recovery quality was significantly better in the Med group.
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Affiliation(s)
- M Paula Larenza Menzies
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Simone K Ringer
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Aude Conrot
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland
| | - Katharina Kluge
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Annette Pn Kutter
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Michelle Jackson
- Clinic for Equine Surgery, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland
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Caslavska J, Koenka IJ, Hauser PC, Thormann W. Validation of CE modeling with a contactless conductivity array detector. Electrophoresis 2016; 37:699-710. [PMID: 26799858 DOI: 10.1002/elps.201500424] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 01/13/2016] [Accepted: 01/14/2016] [Indexed: 11/11/2022]
Abstract
Dynamic computer simulation data are compared for the first time with CE data obtained with a laboratory made system comprising an array of 8 contactless conductivity detectors (C(4) Ds). The experimental setup featured a 50 μm id linear polyacrylamide (LPA) coated fused-silica capillary of 70 cm length and a purpose built sequential injection analysis manifold for fluid handling of continuous or discontinuous buffer configurations and sample injection. The LPA coated capillary exhibits a low EOF and the manifold allows the placement of the first detector at about 2.7 cm from the sample inlet. Agreement of simulated electropherograms with experimental data was obtained for the migration and separation of cationic and anionic analyte and system zones in CZE configurations in which EOF and other column properties are constant. For configurations with discontinuous buffer systems, including ITP, experimental data obtained with the array detector revealed that the EOF is not constant. Comparison of simulation and experimental data of ITP systems provided the insight that the EOF can be estimated with an ionic strength dependent model similar to that previously used to describe EOF in fused-silica capillaries dynamically double coated with Polybrene and poly(vinylsulfonate). For the LPA coated capillaries, the electroosmotic mobility was determined to be 17-fold smaller compared to the case with the charged double coating. Simulation and array detection provide means for quickly investigating electrophoretic transport and separation properties. Without realistic input parameters, modeling alone is not providing data that match CE results.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Peter C Hauser
- Department of Chemistry, University of Basel, Basel, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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41
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Theurillat R, Sandbaumhüter FA, Bettschart-Wolfensberger R, Thormann W. Microassay for ketamine and metabolites in plasma and serum based on enantioselective capillary electrophoresis with highly sulfated γ-cyclodextrin and electrokinetic analyte injection. Electrophoresis 2015; 37:1129-38. [DOI: 10.1002/elps.201500468] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/24/2015] [Accepted: 11/26/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
| | | | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
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Sandbaumhüter FA, Theurillat R, Thormann W. Effects of medetomidine and its active enantiomer dexmedetomidine on N-demethylation of ketamine in canines determined in vitro using enantioselective capillary electrophoresis. Electrophoresis 2015; 36:2703-2712. [PMID: 26104860 DOI: 10.1002/elps.201500147] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 05/29/2015] [Accepted: 06/10/2015] [Indexed: 11/12/2022]
Abstract
Cytochrome P450 (CYP) enzymes catalyze the metabolism of both, the analgesic and anesthetic drug ketamine and the α2 -adrenergic receptor-agonist medetomidine that is used for sedation and analgesia. As racemic medetomidine or its active enantiomer dexmedetomidine are often coadministered with racemic or S-ketamine in animals and dexmedetomidine together with S- or racemic ketamine in humans, drug-drug interactions are likely to occur and have to be characterized. Enantioselective CE with highly sulfated γ-cyclodextrin as chiral selector was employed for analyzing in vitro (i) the kinetics of the N-demethylation of ketamine mediated by canine CYP3A12 and (ii) interactions occurring with racemic medetomidine and dexmedetomidine during coincubation with ketamine and canine liver microsomes (CLM), canine CYP3A12, human liver microsomes (HLM), and human CYP3A4. For CYP3A12 without an inhibitor, Michaelis-Menten kinetics was determined for the single enantiomers of ketamine and substrate inhibition kinetics for racemic ketamine. Racemic medetomidine and dexmedetomidine showed an inhibition of the N-demethylation reaction in the studied canine enzyme systems. Racemic medetomidine is the stronger inhibitor for CLM, whereas there is no difference for CYP3A12. For CLM and CYP3A12, the inhibition of dexmedetomidine is stronger for the R- compared to the S-enantiomer of ketamine, a stereoselectivity that is not observed for CYP3A4. Induction is observed at a low dexmedetomidine concentration with CYP3A4 but not with CYP3A12, CLM, and HLM. Based on these results, S-ketamine combined with dexmedetomidine should be the best option for canines. The enantioselective CE assay with highly sulfated γ-cyclodextrin as chiral selector is an effective tool for determining kinetic and inhibition parameters of metabolic pathways.
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Affiliation(s)
- Friederike A Sandbaumhüter
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Mikkonen S, Thormann W, Emmer Å. Computer simulations of sample preconcentration in carrier-free systems and isoelectric focusing in microchannels using simple ampholytes. Electrophoresis 2015; 36:2386-95. [PMID: 26036978 DOI: 10.1002/elps.201500120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 04/27/2015] [Accepted: 05/12/2015] [Indexed: 01/05/2023]
Abstract
In this work, electrophoretic preconcentration of protein and peptide samples in microchannels was studied theoretically using the 1D dynamic simulator GENTRANS, and experimentally combined with MS. In all configurations studied, the sample was uniformly distributed throughout the channel before power application, and driving electrodes were used as microchannel ends. In the first part, previously obtained experimental results from carrier-free systems are compared to simulation results, and the effects of atmospheric carbon dioxide and impurities in the sample solution are examined. Simulation provided insight into the dynamics of the transport of all components under the applied electric field and revealed the formation of a pure water zone in the channel center. In the second part, the use of an IEF procedure with simple well defined amphoteric carrier components, i.e. amino acids, for concentration and fractionation of peptides was investigated. By performing simulations a qualitative description of the analyte behavior in this system was obtained. Neurotensin and [Glu1]-Fibrinopeptide B were separated by IEF in microchannels featuring a liquid lid for simple sample handling and placement of the driving electrodes. Component distributions in the channel were detected using MALDI- and nano-ESI-MS and data were in agreement with those obtained by simulation. Dynamic simulations are demonstrated to represent an effective tool to investigate the electrophoretic behavior of all components in the microchannel.
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Affiliation(s)
- Saara Mikkonen
- Department of Chemistry, Analytical Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Åsa Emmer
- Department of Chemistry, Analytical Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
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Caslavska J, Mosher RA, Thormann W. Impact of Taylor-Aris diffusivity on analyte and system zone dispersion in CZE assessed by computer simulation and experimental validation. Electrophoresis 2015; 36:1529-38. [PMID: 25820794 DOI: 10.1002/elps.201500034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/03/2015] [Accepted: 03/17/2015] [Indexed: 11/07/2022]
Abstract
Application of pressure-driven laminar flow has an impact on zone and boundary dispersion in open tubular CE. The GENTRANS dynamic simulator for electrophoresis was extended with Taylor-Aris diffusivity which accounts for dispersion due to the parabolic flow profile associated with pressure-driven flow. Effective diffusivity of analyte and system zones as functions of the capillary diameter and the amount of flow in comparison to molecular diffusion alone were studied for configurations with concomitant action of imposed hydrodynamic flow and electroosmosis. For selected examples under realistic experimental conditions, simulation data are compared with those monitored experimentally using modular CE setups featuring both capacitively coupled contactless conductivity and UV absorbance detection along a 50 μm id fused-silica capillary of 90 cm total length. The data presented indicate that inclusion of flow profile based Taylor-Aris diffusivity provides realistic simulation data for analyte and system peaks, particularly those monitored in CE with conductivity detection.
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Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Thormann W, Caslavska J, Mosher RA. Computer simulation of electrophoretic aspects of enantiomer migration and separation in capillary electrochromatography with a neutral selector. Electrophoresis 2015; 36:773-83. [PMID: 25401792 DOI: 10.1002/elps.201400457] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 11/08/2014] [Accepted: 11/11/2014] [Indexed: 11/07/2022]
Abstract
A computer simulation study describing the electrophoretic separation and migration of methadone enantiomers in presence of free and immobilized (2-hydroxypropyl)-β-CD is presented. The 1:1 interaction of methadone with the neutral CD was simulated by using experimentally determined mobilities and complexation constants for the complexes in a low-pH BGE comprising phosphoric acid and KOH. The use of complex mobilities represents free solution conditions with the chiral selector being a buffer additive, whereas complex mobilities set to zero provide data that mimic migration and separation with the chiral selector being immobilized, that is CEC conditions in absence of unspecific interaction between analytes and the chiral stationary phase. Simulation data reveal that separations are quicker, electrophoretic displacement rates are reduced, and sensitivity is enhanced in CEC with on-column detection in comparison to free solution conditions. Simulation is used to study electrophoretic analyte behavior at the interface between sample and the CEC column with the chiral selector (analyte stacking) and at the rear end when analytes leave the environment with complexation (analyte destacking). The latter aspect is relevant for off-column analyte detection in CEC and is described here for the first time via the dynamics of migrating analyte zones. Simulation provides insight into means to counteract analyte dilution at the column end via use of a BGE with higher conductivity. Furthermore, the impact of EOF on analyte migration, separation, and detection for configurations with the selector zone being displaced or remaining immobilized under buffer flow is simulated. In all cases, the data reveal that detection should occur within or immediately after the selector zone.
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Affiliation(s)
- Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Řemínek R, Glatz Z, Thormann W. Optimized on-line enantioselective capillary electrophoretic method for kinetic and inhibition studies of drug metabolism mediated by cytochrome P450 enzymes. Electrophoresis 2015; 36:1349-57. [PMID: 25382218 DOI: 10.1002/elps.201400356] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/24/2014] [Accepted: 11/02/2014] [Indexed: 12/18/2022]
Abstract
Pharmacokinetic and pharmacodynamic properties of a chiral drug can significantly differ between application of the racemate and single enantiomers. During drug development, the characteristics of candidate compounds have to be assessed prior to clinical testing. Since biotransformation significantly influences drug actions in an organism, metabolism studies represent a crucial part of such tests. Hence, an optimized and economical capillary electrophoretic method for on-line studies of the enantioselective drug metabolism mediated by cytochrome P450 enzymes was developed. It comprises a diffusion-based procedure, which enables mixing of the enzyme with virtually any compound inside the nanoliter-scale capillary reactor and without the need of additional optimization of mixing conditions. For CYP3A4, ketamine as probe substrate and highly sulfated γ-cyclodextrin as chiral selector, improved separation conditions for ketamine and norketamine enantiomers compared to a previously published electrophoretically mediated microanalysis method were elucidated. The new approach was thoroughly validated for the CYP3A4-mediated N-demethylation pathway of ketamine and applied to the determination of its kinetic parameters and the inhibition characteristics in presence of ketoconazole and dexmedetomidine. The determined parameters were found to be comparable to literature data obtained with different techniques. The presented method constitutes a miniaturized and cost-effective tool, which should be suitable for the assessment of the stereoselective aspects of kinetic and inhibition studies of cytochrome P450-mediated metabolic steps within early stages of the development of a new drug.
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Affiliation(s)
- Roman Řemínek
- Department of Biochemistry, Faculty of Science and CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic.,Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Zdeněk Glatz
- Department of Biochemistry, Faculty of Science and CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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Liechti FD, Stüdle N, Theurillat R, Grandgirard D, Thormann W, Leib SL. The mood-stabilizer lithium prevents hippocampal apoptosis and improves spatial memory in experimental meningitis. PLoS One 2014; 9:e113607. [PMID: 25409333 PMCID: PMC4237452 DOI: 10.1371/journal.pone.0113607] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 10/28/2014] [Indexed: 12/20/2022] Open
Abstract
Pneumococcal meningitis is associated with high morbidity and mortality rates. Brain damage caused by this disease is characterized by apoptosis in the hippocampal dentate gyrus, a morphological correlate of learning deficits in experimental paradigms. The mood stabilizer lithium has previously been found to attenuate brain damage in ischemic and inflammatory diseases of the brain. An infant rat model of pneumococcal meningitis was used to investigate the neuroprotective and neuroregenerative potential of lithium. To assess an effect on the acute disease, LiCl was administered starting five days prior to intracisternal infection with live Streptococcus pneumoniae. Clinical parameters were recorded, cerebrospinal fluid (CSF) was sampled, and the animals were sacrificed 42 hours after infection to harvest the brain and serum. Cryosections of the brains were stained for Nissl substance to quantify brain injury. Hippocampal gene expression of Bcl-2, Bax, p53, and BDNF was analyzed. Lithium concentrations were measured in serum and CSF. The effect of chronic lithium treatment on spatial memory function and cell survival in the dentate gyrus was evaluated in a Morris water maze and by quantification of BrdU incorporation after LiCl treatment during 3 weeks following infection. In the hippocampus, LiCl significantly reduced apoptosis and gene expression of Bax and p53 while it increased expression of Bcl-2. IL-10, MCP-1, and TNF were significantly increased in animals treated with LiCl compared to NaCl. Chronic LiCl treatment improved spatial memory in infected animals. The mood stabilizer lithium may thus be a therapeutic alternative to attenuate neurofunctional deficits as a result of pneumococcal meningitis.
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Affiliation(s)
- Fabian D. Liechti
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Nicolas Stüdle
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Denis Grandgirard
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephen L. Leib
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Biology Division, Spiez Laboratory, Swiss Federal Office for Civil Protection, Spiez, Switzerland
- * E-mail:
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Thormann W, Chankvetadze L, Gumustas M, Chankvetadze B. Dynamic computer simulation of electrophoretic enantiomer migration order and separation in presence of a neutral cyclodextrin. Electrophoresis 2014; 35:2833-41. [DOI: 10.1002/elps.201400193] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Wolfgang Thormann
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
| | - Lali Chankvetadze
- Department of Physical and Analytical Chemistry; School of Exact and Natural Sciences; Tbilisi State University; Tbilisi Georgia
| | - Mehmet Gumustas
- Department of Physical and Analytical Chemistry; School of Exact and Natural Sciences; Tbilisi State University; Tbilisi Georgia
| | - Bezhan Chankvetadze
- Department of Physical and Analytical Chemistry; School of Exact and Natural Sciences; Tbilisi State University; Tbilisi Georgia
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Theurillat R, Larenza MP, Feige K, Bettschart- Wolfensberger R, Thormann W. Development of a method for analysis of ketamine and norketamine enantiomers in equine brain and cerebrospinal fluid by capillary electrophoresis. Electrophoresis 2014; 35:2863-9. [DOI: 10.1002/elps.201400093] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/07/2014] [Accepted: 04/21/2014] [Indexed: 11/06/2022]
Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
| | - M. Paula Larenza
- Equine Department; Vetsuisse Faculty; University of Zürich; Zürich Switzerland
| | - Karsten Feige
- Clinic for Horses; University of Veterinary Medicine; Hannover Germany
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
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Caslavska J, Joneli J, Wanzenried U, Schiess J, Lanz C, Thormann W. Determination of genetic transferrin variants in human serum by high-resolution capillary zone electrophoresis†. J Sep Sci 2014; 37:1663-70. [DOI: 10.1002/jssc.201400243] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/08/2014] [Accepted: 04/08/2014] [Indexed: 12/17/2022]
Affiliation(s)
- Jitka Caslavska
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
| | - Jeannine Joneli
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
| | - Ursula Wanzenried
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
| | - Jeannette Schiess
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
| | - Christian Lanz
- Laboratory of Phytopharmacology, Bioanalytics and Pharmacokinetics; Department of Clinical Research; University of Bern; Bern Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; Institute for Infectious Diseases; University of Bern; Bern Switzerland
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